(a) Field of the Invention
The present invention relates to an improved door structure, especially to the improvements made on a structure of fireproof doors, entrance doors, emergency doors, and acoustical isolation doors. The improved door structure has better performances in protection against fires, smoke and acoustical penetration. It can give better security to prevent invasion.
(b) Description of the Prior Art
Conventional door structures adopt right corners on the periphery of door leaves and door frames. Such door structures are easier to be opened by inserting a tool into the gaps between a door leaf and its door frame to pry the door open. In addition, when external forces hit such a door structure, the door leaf and the door frame deform easier. Furthermore, if chain locks and do or hinges loosen due to destruction by external forces or rustiness, the door leaf of a conventional door structure will easily separate from the door frame and fall flat, which might produce casualties. Such possibilities must be eliminated, especially for children. Moreover a metal door will expand when heated. Thus when the house is on fire, the door leaf and the door frame will deform. The right corner design of conventional door structures makes the door leaf and the door frame stuck to each other easier. This may lead to the blockade of emergency exits. Besides, conventional door structures often allow gaps between the boundaries of a door leaf and a door frame to make opening easier and smooth. The gaps are detrimental to the effect of preventing smoke penetration. Conventional door structures are provided with lock means to join a door leaf with a door frame when door is closed to prevent thief's or stranger's invasion. The lock means should be preferably provided with features of preventing destruction by external forces. Conventional door structures usually have one single lock or latch. Such lock means are easier to be broken. As a result they can not provide better protection against the invasion.